Researchers at Imperial College have achieved a groundbreaking feat by generating a spinning disk of plasma in a laboratory setting. This remarkable accomplishment allows for a more faithful emulation of the plasma disks that encircle black holes and give rise to the formation of stars.
By replicating the behavior of matter as it approaches a black hole and transforms into plasma—an ionized state consisting of charged particles and free electrons—scientists can gain invaluable insights into the growth of black holes and the processes involved in the creation of stars through the collapse of matter.
The formation of an accretion disk, characterized by the rotation of plasma, occurs as matter nears a black hole. This rotation induces a centrifugal force that drives the plasma outward, counteracted by the gravitational pull exerted by the black hole.
However, a significant predicament arises when contemplating these luminous rings of orbiting plasma: how does a black hole grow if the material remains trapped in orbit rather than plunging into the black hole itself? According to the leading theory, magnetic field instabilities within the plasma induce friction, causing it to lose energy and eventually succumb to the gravitational pull of the black hole.
To investigate this theory, scientists have traditionally employed liquid metals that can be set in motion while subjecting them to magnetic fields. Nonetheless, due to the necessity of confining the metals within pipes, this approach fails to accurately replicate the behavior of freely flowing plasma.
In a groundbreaking experiment, the researchers at Imperial College leveraged their state-of-the-art Mega Ampere Generator for Plasma Implosion Experiments machine (MAGPIE) to achieve the spinning of plasma, providing a more precise representation of accretion disks. The detailed findings of this study were published in the esteemed journal Physical Review Letters on May 12.
The lead author of the study, Dr. Vicente Valenzuela-Villaseca, conducted this research as part of his Ph.D. program in the Department of Physics at Imperial College. Dr. Valenzuela-Villaseca emphasized the significance of comprehending the behavior of accretion disks, stating that it not only sheds light on the growth of black holes but also offers insights into the collapse of gas clouds that give birth to stars. Furthermore, understanding the stability of plasmas in fusion experiments can aid in the effective creation of artificial stars.
The researchers employed the MAGPIE machine to propel and collide eight plasma jets, resulting in the formation of a spinning column. They made a noteworthy observation that the inner regions of the spinning ring moved at a higher velocity, a crucial characteristic observed in accretion disks throughout the universe.
Due to the nature of MAGPIE, which generates short plasma pulses, the experiment could only capture approximately one rotation of the disk. Nevertheless, this proof-of-concept study demonstrates the potential for increasing the number of rotations by utilizing longer pulses, thereby enabling a more comprehensive understanding of the disk’s properties. Extending the duration of the experimental run would also facilitate the application of magnetic fields to assess their impact on the system’s friction.
Dr. Valenzuela-Villaseca expressed optimism about the future prospects, stating that we are merely scratching the surface of new ways to examine accretion disks. This includes conducting experiments like theirs and capturing snapshots of black holes using instruments like the Event Horizon Telescope. These advancements will enable scientists to test their theories against astronomical observations and ascertain their validity.
Source: Imperial College London